A Force Variation Machine (FVM) is commonly used within the tire industry for measuring tire uniformity in order to insure that manufactured tires are within run-out limits. Commercial FVM units utilize sensors to measure and verify that tires are within lateral run-out, radial run-out, and sidewall bulge and valley limits. The sensors deployed may be laser non-contact or contact devices. When positioned at known locations to a tire, the sensors deploy a laser beam against the tire to determine whether the tire conforms to tire specifications or must be scrapped.
It is imperative, therefore, that sensors employed in FVM be accurate and dependable. Without a method and apparatus for verifying the accuracy of the non-contact sensors on FVMs, it is not possible to determine whether tires within run-out limits are being scrapped or tires not within run-out limits are being passed. Quality control becomes problematic if improperly calibrated sensors are utilized.
Currently, run-out sensors for FVMs are calibrated using “check tires”. Check tires are constructed using existing rubber building machinery and methods. While care is exercised in the production of a check tire, the check tires still may be inhomogeneous and non-uniform and such tires may not possess consistent run-out. As a result, check tire non-uniformity may influence the accuracy of FVM run-out sensor calibration. Due to inaccuracies in verifying run-out sensor calibration using current check tire practices, a possibility exists that tires continue to be scrapped when technically within acceptable run-out limits and other tires will not be scrapped when run-out is outside of acceptable limits. There remains, accordingly, a need for a more accurate means of verifying the calibration of the run-out sensors on FVMs.